High levels of dRYBP induce apoptosis in Drosophila imaginal cells through the activation of reaper and the requirement of trithorax, dredd and dFADD

Abstract

Drosophila RYBP (dRYBP; Ring1 and YY1 Binding Protein) is a Polycomb and trithorax interacting protein, whose homologous RYBP/DEDAF mammalian counterparts exhibit tumor cell-specific killing activity. Here we show that although endogenous dRYBP is not involved in developmental apoptosis, high levels of exogenous dRYBP induce apoptosis in all the imaginal discs of the fly, indicating that dRYBP apoptotic activity is not specific to tumor cells. We also show that dRYBP-induced apoptosis is inhibited by high levels of either p35 or DIAP1 (Drosophila Inhibitor of Apoptosis Protein 1), and requires the function of the pro-apoptotic REAPER, HID and GRIM proteins, the apical caspase DREDD, the adaptor dFADD protein as well as TRITHORAX (TRX), an epigenetic transcriptional regulator. Furthermore, we demonstrate that overexpression of TRX also induces apoptosis in the imaginal discs. Finally, we show that the expression of reaper-lacZ is upregulated both upon dRYBP-induced apoptosis and upon TRXinduced apoptosis in imaginal discs and that the reaper gene is a direct target of dRYBP in Drosophila embryos. Our results indicate that dRYBP triggers in a receptor-mediated apoptotic pathway that also includes TRX-dependent epigenetic regulation of gene expression.

Alu Elements in ANRIL Non-Coding RNA at Chromosome 9p21 Modulate Atherogenic Cell Functions through Trans-Regulation of Gene Networks

“…ANRIL did not bind to CoREST/REST repressor proteins but bound to PRC1 proteins CBX7and RING1B and to PRC2 proteins EED, JARID2, RBAP46, and SUZ12. ANRIL also bound to PRC-associated proteins RYBP and YY1 which have been shown to induce gene expression [29], [30]. To investigate genome-wide distribution of Polycomb complexes, we chose CBX7 [3] and SUZ12 [20] as representative PcG proteins and performed chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) in ANRIL2 cells.…”

“…Moreover, Morey et al demonstrated reduced gene repression in distinct PRC1 compexes containing RYBP, which was shown to associate with ANRIL (Figure 3) [42]. Alternatively, ANRIL -bound activating factors RYBP and YY1 may directly activate gene expression [29], [30] or ANRIL might bind other activating epigenetic effector proteins [43]. Taken together, we demonstrate a central role of PRC1 and PRC2 but not CoREST/Rest in ANRIL -mediated repression and induction of genes but additional work is clearly warranted to unravel the complex nature of these trans -regulatory mechanisms.…”

“…We demonstrated binding to predominantly inhibitory (CBX7, RING1B, EED, JARID2, RBAP46, SUZ12) [41] and potentially activating factors (RYBP, YY1) [29], [30]. CBX7 and SUZ12 were selected as representative proteins for PRC1 and 2, respectively, and were followed up in genome-wide ChIP-seq experiments (Figure 3 and Figure 4).…”

dRYBP Contributes to the Negative Regulation of the Drosophila Imd Pathway

“…RNA extraction and RT reactions were performed as previously described [31]. qRT-PCR was performed using FastStart Universal SYBR Green MasterRox (Roche) in an Applied Biosystems 7900 Sequence Detector System.…”

“…Human RYBP/DEDAF has been shown to interact with DED ( D eath E ffector D omain) containing proteins [35], [36] that mediate homotypic interactions important for the assembly and activation of apoptotic and inflammatory complexes [37]. In Drosophila , high levels of dRYBP induces apoptosis in imaginal disc cells and this apoptosis is dependent on dFADD and DREDD [31], two DED containing proteins [37] also involved in the IMD-mediated immune response in Drosophila [10]–[12].…”